Mayor Bloomberg has become the first person in US history to spend $100 million out of his own pocket to win municipal office.

His campaign yesterday released figures that showed the mayor burned through $102.1 million — and counting — to eke out a third-term victory over underfunded city Comptroller Bill Thompson.

The filings revealed that Bloomberg spent $18.7 million beginning Oct. 20 in the run-up to Election Day — more than $1 million a day.

Since he got just 585,466 votes — nearly 200,000 fewer than in 2005 — Bloomberg’s win by just 4.6 percentage points has, so far, cost him $174 a vote.

And this latest filing doesn’t even include the fat bonuses he has historically doled out to top aides at the end of the campaign year. If he does so again this time, they would be revealed in the January campaign filings.

By contrast, Thompson, whose filing is due Monday, is expected to have spent less than $10 million.

Advocates of campaign finance reform were quick to slam the mayor’s outsize expenditures.

“It’s beyond embarrassing,” declared Susan Lerner, executive director of Common Cause New York. “These are astronomical figures. They’re higher than the budgets of a lot of cities.”

But Howard Wolfson, the mayor’s campaign spokesman, defended the seemingly over-the-top spending as necessary at a time when voters were in a mood to kick out incumbents.

“Losing is embarrassing,” Wolfson said. “We recognized the strong national anti-incumbent mood early and ensured that we overcame it.”

Bloomberg — the wealthiest man in New York, with an estimated net worth of $17 billion — has now rung up an astonishing $261 million in campaign bills since he first ran for office in 2001.

The release of the figures yesterday afternoon, one day after Thanksgiving, was designed to dampen publicity as much as possible, Lerner charged, saying: “They’re trying to hide it, and they can’t.”

As in Bloomberg’s past campaigns, no expense was spared. Staff and volunteers, for example, were treated to free beverages and snacks — at a cost of $34,679 for the 38-day filing period, or nearly $1,000 a day.

Then there’s Sara Molinaro, granddaughter of Staten Island Borough President James Molinaro, one of the mayor’s closest allies. She was hired at a salary of $2,311 twice a month — the equivalent of $55,464 a year.

That’s more than the $48,000 a year paid to Rudolph S. Giuliani, a cousin of former Mayor Rudy Giuliani, who also endorsed Bloomberg.

The campaign also forked over $11,197 to AA Writing Services, of upstate Monroe, for what Wolfson described as Yiddish translation services.

Even the city treasury got a piece of the action — when a staff member’s car was towed and the campaign anted up the $185 fee.

As for the lowest listed expense in the filings, that honor went to staff member Jennifer Jong — who was reimbursed $1.90 for supplies she purchased at the 99 Cents Wonder store in upper Manhattan.